Surveillance is the monitoring of activities or other changing information, usually the behavior of people, for the purpose of influencing, managing, directing, or protecting. Government and law-enforcement agencies, as well as other authorities, often use surveillance to recognize and monitor threats, investigate criminal activity, and maintain social control. Surveillance devices, such as closed circuit or securely networked video cameras, are typically used by authorities to monitor a particular area. Often the installation of such surveillance devices serves as a deterrent for criminal behavior. Examples include the installation of video cameras to monitor busy public spaces, such as Times Square in New York, or inside or outside of retail shops.
Unrelated to the field of surveillance, solar power has been used to power a number of small and medium-sized applications. Examples include applications ranging from a calculator using a single solar cell to off-the-grid homes using an array of solar cells to supply power. Solar power is the conversion of light into electricity, typically converted directly using photovoltaics (PVs), which convert light into electricity using the photoelectric effect. Solar power is seen as an environmentally friendly and clean energy source. Now, many traffic lights and traffic cameras and even public trash receptacles take advantage of their outdoor location and access to sunlight by using solar power to operate.